Photosensitive elements are extremely useful in the preparation of printing plates such as relief or lithographic plates, photoresists, etc. These photosensitive elements may be photopolymer, silver halide, diazo or other types of light-sensitive materials. All require for their imagewise exposure an article referred to as a phototool, which is a copy of the image to be reproduced. Generally the phototool is a flexible photographic element which is cheap and easy to produce. The photographic element accurately copies the image to be reproduced. This is extremely important in printing and particularly in the preparation of photoresists used to manufacture printed circuits where tolerances are extremely critical. During the preparation of a printed circuit, for example, the photoresist is imagewise exposed to actinic radiation through the phototool. Not only is heat generated but the relative humidity of the room where the exposure is taking place may change radically. It is absolutely imperative to insure accurate registration during the exposure step or steps, since the phototool is normally reused many times over the period of a day. It is imperative that the photosensitive element phototool maintain a constant size with distortion limited to 0.001 inch (0.025 mm) or less over 24 inches (60.96 cm) with a .+-.5% change in Relative Humidity. In order to maintain the distortion level below the established limit especially when using conventional silver halide photographic film elements, it is necessary to accurately control the humidity since these elements absorb moisture from the air and within a short period of time, e.g., 1 to 2 hours or less, can exceed this established distortion limit.
There is a need for a photosensitive element which limits dimensional change to no more than 0.001 inch (0.025 mm) per 24 inches (60.96 cm) within six hours after exposure to a .+-.5% Relative Humidity change.